greylistd CouchDB support

Add CouchDB support to greylistd to support storing triplets in database rather then a plaintext file.

This allows quicker lookups and replication to other greylistd instances.

Writing this patch was started by lefant.net and I continued his work.

Checkout also Fabian's couchapp from github !

• Homepage: http://slett.net/spam-filtering-for-mx/exim-greylisting.html